Phase shifter using two voltage sensitive elements



June 22, 1965 H. c. RUDD, JR., ETAL 3,191,130

PHASE SHIFTER USING TWO VOLTAGE SENSITIVE ELEMENTS Filed May 31, 1963 AC REFERENCE SIGNAL k7? 5/ 6/ ins: /3 l4 SHIFTED Ac SIGNAL 0c VOLTAGE VOLTAGIITSTENSITIVE VARIABLE CAPACITOR INVENTORS HARRY a. RUDD JR. WALTER J. M02025 ATTORNEY United States Patent 3,191,130 1 PHASE SHIFTER USING TWO VOLTAGE SENSITKVE ELEMENTS Harry C. Rudd, in, St. Petersburg, Fla., and Walter J. Mozdzen, College Park, Md., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed May 31, 1963, Ser. No. 284,765

5 (Ilaims. (Cl. 332-29) This invention relates to phase shifters and more particularly to voltage sensitive variable phase shifters.

The phase shifting circuits developed in the prior art, although quite advantageous for most applications, have the limitation that an incoming signal of constant amplitude can be shifted only through a fixed phase angle. The present invention overcomes this limitation.

The present invention has the capability of shifting a constant amplitude waveform through a range of phase angles automatically. By using voltage sensitive impedance elements in combination with an active element, a voltage sensitive automatic variable phase shifter is provided for shifting a waveform in accordance with a DC. signal applied thereto.

An object of this invention is the provision of a variable phase shifter.

A further object of the invention is the provision of an automatic variable phase shifter.

A still further object of this invention is to provide a constant amplitude signal with a variable phase shift.

An additional object is the provision of a voltage sensitive phase modulation system.

Another object is to delay or shift a constant amplitude A signal through a specified range of phase angles.

Various other objects and features of the invention will hereinafter be more fully apparent from the following description of the drawing which will illustrate one embodiment of the invention. The embodiment disclosed is illustrative of the invention but is in no way intended to limit the invention as defined by the appended claims.

Referring now to the single figure of drawing which illustrates the invention, there is shown a first input terminal 11 having one end of a capacitor 12 connected thereto and a second input terminal 13 having one end of an inductor 14 connected thereto. The other ends of the capacitor and inductor are tied together at terminal 15. An electron discharge device or transistor 21 has its base electrode 22 connected to the terminal the emitter terminal 23 is connected to one terminal of a voltage sensitive variable capacitor 31 for example a varicap; and the collector terminal 24 is connected to one terminal of a voltage sensitive variable resistor 01' varistor 41. The other terminals of the voltage sensitive variable capacitor and varistor are tied together at terminal 51. A coupling capacitor 61 is connected to the terminal 51 while the other end serves as the output terminal 62 of the device. Suitable biasing for the device 21 is provided by the fixed and settable resistors 71 through 76 and the D.C. potential applied at terminals 77 and 78.

The varistor 41 may be one of any of the numerous devices, generally two electrode semiconductor elements whose resistance varies with the voltage applied thereto. In the illustrated embodiment, the characteristic voltagecurrent curve is linear. Many devices exhibiting the features described hereinbefore are available, the most common of which are made of silicon carbide compounds. There are other varistors manufactured whose resistance varies in response to the current or polarity of the applied signal. All of the devices described herein may exhibit non-linear characteristics as well.

The voltage sensitive variable capacitor 31, similarly, is a commercially available element whose capacitance value varies with the signal applied.

If there is an increasing potential across the varistor and voltage sensitive variable capacitor, the resistance and capacitance decrease accordingly whereby there is an increase in the capacitive reactance and a decrease in resistance, thus causing a phase shift to an incoming signal, such phase shift being linear, and may be an angle of as much as The signal to be shifted is applied at terminal 11, through capacitor 12 which of course passes only the AC. component of the signal. Similarly, a D.C. potential is applied at input 13 through the inductor 14 which isolates this potential from any spurious A.C. signals. The bias on the transistor 21, maintained by means of resistors 72 and 75, is of such a nature that the collector 24 is kept positive with respect to the emitter 23. The biasing resistors 71, 73, 74, and 76 are adjusted to maintain a constant voltage across the varistor and voltage sensitive variable capacitor so that the output terminal is at approximately ground thereby allowing the collector and emitter to always be positive and negative, respectively, with respect to the output.

Of course, by referring to the characteristic curves of the voltage sensitive variable capacitor and varistor the bias may be set at an optimum point. Of necessity, to prevent output distortion, the input signal amplitudes are kept small and therefore have no deleterious effect on the biasing.

As the DC. signal applied increases, for example, positively, this causes the terminal 15, the base of the transistor, to become more positive, the terminal 23, the emitter, more positive; and the terminal 24, the collector, more negative; all with respect to terminal 51. The result of such an action causes the voltage sensitive variable capacitor and varistor to increase in value and thereby causes an increase in resistance and a decrease in capacitive reactance whereby the phase angle of the AC. input is changed.

Of course, if the DC. level is decreased the phase angle changes in the opposite direction. It is thus possible to change the phase angle of the AC. signal :by as much as plus or minus forty-five degrees (i45).

Obviously, if the output terminal 62 is tied to the input terminal 11 of a duplicate device, an additional 45 phase change is possible, providing a total possible shift of i90. The terminals 13, of both devices, may be tied to the same controlled DC. source,

It is a further capability of the present invention to provide phase modulation. For example, if the DO. input signal carries amplitude information such as a binary signal, two levels of DC, or a decimal signal, ten levels of DC, by maintaining the A.C signal at a constant amplitude, the DC. is phase modulated and thereby converted to information impressed upon the AC. carrier or phase modulated information.

The condition responsive elements, the varistor 41 and voltage sensitive variable capacitor 31, may be replaced by current or polarity sensitive similar elements to provide a current or polarity sensitive phase shifter.

A new and improved variable phase shifter has been described which is voltage, current or polarity sensitive, which will shift or modulate an incoming signal of con stant amplitude through a phase angle of 90.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

ing: 7 I

(a) an electron discharge device having at lea st three ing:

a n v v3 j 1. A voltage-sensitive variable phase shifter compristerminals (b) a first condition responsive element connected to one of said terminals 7 i i n V (c) a second condition responsive element connected to a second of said terminals, said first cond tion respon siveelement' exhibiting differentimpedance charac v H 10 terist ics from said second condition responsive .ele-

' ment, whereby onesignal applied to a third of said '(a) said electron discharge device is a semiconductor. 4. The phase shifter :of claim 2 wherein: n

(a) said electron discharge device is a transistor. p 5. A voltage sensitive variable phase shifterxcompris (a). a transistor having I (1) a base electrode (2) an emitter electrode (3) and a collector electrode; 7 (b) a fixed capacitor having one end connected to said haseand having another'end to which an A.C. voltage signal is applied; i

(c) a fixed inductor having one end connected to the terminal defined by said base and said one end of said capacitor and having another end to which a DC.

. voltage is applied; 7

(d) a second fixed capacitor having a first terminal and a second terminal, said second terminal serving as an output for said phase shifter; I

(e) a voltage sensitive variable capacitorhaving a first terminal connected to said emitter and having a second terminal "connected to said first terminal .of

i said second fixed capacitor;

(f) a voltage sensitive resistor having a first terminal connected to saidcollector and a second terminal connected tothe terminal defiiied by the connection between {said'second terminal of said variable capacitor and said first terminal of saidsecond capacitor whereby said A.C. signal is shifted through a preselected phase angle which may be as much as 90, dependent upon the amplitude of said D.C., signal.

V References Cited by the Examiner Low-Frequency Phase-Shift Modulator-Coombs, Elec- 25 tronic's, December l954, pp. 1198 200, 202 Figure 2.

ROY LAKE, Primary Examiner. ALFRED L. BRODY, Examiner. 

1. A VOLTAGE SENSITIVE VARIABLE PHASE SHIFTER COMPRISING: (A) AN ELECTRON DISCHARGE DEVICE HAVING AT LEAST THREE TERMINALS (B) A FIRST CONDITION RESPONSIVE ELEMENT CONNECTED TO ONE OF SAID TERMINALS (C) A SECOND CONDITION RESPONSIVE ELEMENT CONNECTED TO A SECOND OF SAID TERMINALS, SAID FIRST CONDITION RESPONSIVE ELEMENT EXHIBITING DIFFERENT IMPEDANCE CHARACTERISTICS FROM SAID SECOND CONDITION RESPONSIVE ELEMENT, WHEREBY ONE SIGNAL APPLIED TO A THIRD OF SAID TERMINALS IS PHASE SHIFTED IN ACCORDANCE WITH ANOTHER SIGNAL APPLIED TO SAID THIRD TERMINAL. 